README.rst

ImageKit is a Django app for processing images. Need a thumbnail? A
black-and-white version of a user-uploaded image? ImageKit will make them for
you. If you need to programatically generate one image from another, you need
ImageKit.

ImageKit comes with a bunch of image processors for common tasks like resizing
and cropping, but you can also create your own. For an idea of what's possible,
check out the Instakit project.

For the complete documentation on the latest stable version of ImageKit, seeImageKit on RTD.

Installation

Install PIL or Pillow. (If you're using an ImageField in Django,
you should have already done this.)

If you've never seen Pillow before, it considers itself a
more-frequently updated "friendly" fork of PIL that's compatible with
setuptools. As such, it shares the same namespace as PIL does and is a
drop-in replacement.

Usage Overview

Specs

You have one image and you want to do something to it to create another image.
But how do you tell ImageKit what to do? By defining an image spec.

An image spec is a type of image generator that generates a new image
from a source image.

Defining Specs In Models

The easiest way to use define an image spec is by using an ImageSpecField on
your model class:

As you can probably tell, ImageSpecFields work a lot like Django's
ImageFields. The difference is that they're automatically generated by
ImageKit based on the instructions you give. In the example above, the avatar
thumbnail is a resized version of the avatar image, saved as a JPEG with a
quality of 60.

Sometimes, however, you don't need to keep the original image (the avatar in
the above example); when the user uploads an image, you just want to process it
and save the result. In those cases, you can use the ProcessedImageField
class:

This is pretty similar to our previous example. We don't need to specify a
"source" any more since we're not processing another image field, but we do need
to pass an "upload_to" argument. This behaves exactly as it does for Django
ImageFields.

Note

You might be wondering why we didn't need an "upload_to" argument for our
ImageSpecField. The reason is that ProcessedImageFields really are just like
ImageFields—they save the file path in the database and you need to run
syncdb (or create a migration) when you add one to your model.

ImageSpecFields, on the other hand, are virtual—they add no fields to your
database and don't require a database. This is handy for a lot of reasons,
but it means that the path to the image file needs to be programmatically
constructed based on the source image and the spec.

Defining Specs Outside of Models

Defining specs as models fields is one very convenient way to process images,
but it isn't the only way. Sometimes you can't (or don't want to) add fields to
your models, and that's okay. You can define image spec classes and use them
directly. This can be especially useful for doing image processing in views—
particularly when the processing being done depends on user input.

It's probably not surprising that this class is capable of processing an image
in the exact same way as our ImageSpecField above. However, unlike with the
image spec model field, this class doesn't define what source the spec is acting
on, or what should be done with the result; that's up to you:

Using Specs In Templates

If you have a model with an ImageSpecField or ProcessedImageField, you can
easily use those processed image just as you would a normal image field:

<imgsrc="{{ profile.avatar_thumbnail.url }}" />

(This is assuming you have a view that's setting a context variable named
"profile" to an instance of our Profile model.)

But you can also generate processed image files directly in your template—from
any image—without adding anything to your model. In order to do this, you'll
first have to define an image generator class (remember, specs are a type of
generator) in your app somewhere, just as we did in the last section. You'll
also need a way of referring to the generator in your template, so you'll need
to register it.

You can register your generator with any id you want, but choose wisely!
If you pick something too generic, you could have a conflict with another
third-party app you're using. For this reason, it's a good idea to prefix
your generator ids with the name of your app. Also, ImageKit recognizes
colons as separators when doing pattern matching (e.g. in the generateimages
management command), so it's a good idea to use those too!

Warning

This code can go in any file you want—but you need to make sure it's loaded!
In order to keep things simple, ImageKit will automatically try to load an
module named "imagegenerators" in each of your installed apps. So why don't
you just save yourself the headache and put your image specs in there?

Now that we've created an image generator class and registered it with ImageKit,
we can use it in our templates!

generateimage

The most generic template tag that ImageKit gives you is called "generateimage".
It requires at least one argument: the id of a registered image generator.
Additional keyword-style arguments are passed to the registered generator class.
As we saw above, image spec constructors expect a source keyword argument, so
that's what we need to pass to use our thumbnail spec:

Comparing this syntax to the generateimage tag above, you'll notice a few
differences.

First, we didn't have to specify an image generator id; unless we tell it
otherwise, thumbnail tag uses the generator registered with the id
"imagekit:thumbnail". It's important to note that this tag is *not* using the
Thumbnail spec class we defined earlier; it's using the generator registered
with the id "imagekit:thumbnail" which, by default, is
imagekit.generatorlibrary.Thumbnail.

Second, we're passing two positional arguments (the dimensions and the source
image) as opposed to the keyword arguments we used with the generateimage tag.

Like with the generateimage tag, you can also specify additional HTML attributes
for the thumbnail tag, or use it as an assignment tag:

Using Specs in Forms

In addition to the model field above, there's also a form field version of the
ProcessedImageField class. The functionality is basically the same (it
processes an image once and saves the result), but it's used in a form class:

The benefit of using imagekit.forms.ProcessedImageField (as opposed to
imagekit.models.ProcessedImageField above) is that it keeps the logic for
creating the image outside of your model (in which you would use a normal Django
ImageField). You can even create multiple forms, each with their own
ProcessedImageField, that all store their results in the same image field.

Processors

So far, we've only seen one processor: imagekit.processors.ResizeToFill. But
ImageKit is capable of far more than just resizing images, and that power comes
from its processors.

Processors take a PIL image object, do something to it, and return a new one.
A spec can make use of as many processors as you'd like, which will all be run
in order.

The imagekit.processors module contains processors for many common
image manipulations, like resizing, rotating, and color adjustments. However,
if they aren't up to the task, you can create your own. All you have to do is
define a class that implements a process() method:

Note that when you import a processor from imagekit.processors, imagekit
in turn imports the processor from PILKit. So if you are looking for
available processors, look at PILKit.

Admin

ImageKit also contains a class named imagekit.admin.AdminThumbnail
for displaying specs (or even regular ImageFields) in the
Django admin change list. AdminThumbnail is used as a property on
Django admin classes:

AdminThumbnail can even use a custom template. For more information, see
imagekit.admin.AdminThumbnail.

Management Commands

ImageKit has one management command—generateimages—which will generate cache
files for all of your registered image generators. You can also pass it a list
of generator ids in order to generate images selectively.

Community

Please use the GitHub issue tracker
to report bugs with django-imagekit. A mailing list
also exists to discuss the project and ask questions, as well as the official
#imagekit channel on Freenode.

Contributing

We love contributions! And you don't have to be an expert with the library—or
even Django—to contribute either: ImageKit's processors are standalone classes
that are completely separate from the more intimidating internals of Django's
ORM. If you've written a processor that you think might be useful to other
people, open a pull request so we can take a look!